It is known to prepare o-nitrobenzaldehyde starting from o-nitrotoluene and from an alkyl-oxalate, in the presence of an alcoholate, thereby obtaining o-nitrophenylpyrruvic acid, which is then oxidized with sodium hypochlorite, in order to get the corresponding benzal chloride, subsequently hydrolized to the corresponding aldehyde; such process is quite burdensome because of the necessity of using a three-step reaction and of the presence of an alcoholate. A photochemical bromination of o-nitrotoluene to the corresponding benzal bromide and subsequent alkaline hydrolysis of the bromide were also described, but this method proved to be of very little practical interest because benzal bromide can explode and because of the non-selectivity of the bromination reaction.
One object of the invention is that of providing a simple and cheap process for the preparation of o-nitrobenzaldehyde by oxidation of o-nitrotoluene with an oxidizing agent which can easily be regenerated at the end of the reaction and which may then be repeatedly re-used. Another object is that of providing a process ensuring a very good selectivity to o-nitrobenzaldehyde and satisfactory yields with respect to the oxidizing agent. A still further object is that of providing a process that can be carried out under mild temperature conditions, within short operational times and as a continuous cycle.